Temperature compensation for electric instruments



R. H. SULLIVAN.

TEMPERATURE COMPENSATION EoR ELECTRIC INSTRUMENTS.

APPLICATION FILED DEC. 16, 1919.

Patented Apr. 4, 1922.

LOA/ TEMP COE/f' HIGH TEN/'i COE/z' LOW' TEMP COE/' 'State of New York,

UNITED STATES PATENT OFFICE.

RAYMOND H. SULLIVAN, OF ROCHESTER, NEW YORK, ASSIGNOR T NORTH EAIST ELECTRIC COMPANY, 0F YORK.

ROCHESTER, NEW YORK, A CORPORATION OF NEW TEMPERATURE COMPENSATION .'ElOR ELECTRIC INSTRUMENTS.

Specification of Letters Patent.

Patented Apr. 4, 1922.

Application led December 16, 1919. Serial No. 345,369.

To all lwhom it may concern.'

Be it known that I, RAYMOND H. SULLI- VAN, a citizen ofthe United States, residing at Rochester, in the county of Monroe and have invented certain new and useful Improvements in Temperature Compensation for Electric Instruments;

I and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in thc art to which it appertains to make and use the same.

This invention relates to means by which the effect of varying temperature, upon the action of an "electro-magnetic instrument such as a relayv or an-automatic regulator for a dynamo, may be neutralized, either in part or completely, or even over-compensated if desired.

The object of the invention is to accomplish the desired compensation solely by means of suitably balanced resistances of different temperature-coefiicients, and particularly to avoid the necessity of using inordinate amounts of resistance or materials having `either negative or unusually high temperature coefficients.

It has been proposed to accomplish the result in question by means` of a resistance in series with the winding which is to be compensated, and a second resistance in parallel therewith, the first of these resistances having a low or approximately O coefficient and the second havingv a coefficient higher than that of the winding. This arrangement, while theoretically correct, is impractical for most uses because if the winding is of' copper, which is the only-satisfactory material for commercial purposes, it is impossible to find any material having a sufficiently higher coefficient for use in the parallel resistance. Where the winding is of copper, therefore compensation can be secured in the manner described only by the use of an vinordinate amount of resistance in all arts ofthe system.y

he present invention is a novel arrange- Vment of resistances by which a winding of copper wire may be compensated by the use of a moderate amount of. resistance, and without the necessity of using any material having a higher coefiicient than that of copper. This 1s accomplished by the expedient of lowering' the temperature coefficient, as a whole, of that branch of the circuit including the winding, by introducing into that'b'ranch, in series with the winding, a resistance having a lower coefficient than that of the winding'.

By the arrangement just described several valuable practical results are secured. In the first place, onlyv a moderate amount ot' reslstance need -be used. In the Second place, the branch of the circuit in parallel..

with the winding need not have a higher coefficient than that of the winding, but may,

defined in the annexed claims.

The drawing is a diagram showing the application of the invention to a relay used in regulating the voltage of a dynamoelectric machine.4

The invention is shown as applied to the compensation of a relay-or regulating-device having an electro-magnet 1 provided with a winding 2, which may be of ordinary copper wire. The armature 3 of the relay controls a .short-circuit 4 around a regulating resistance 5. This resistance is connected in series with the shunt field-winding 6 of a dynamo 7, while the winding 2 of the relay is connectedthrough compensating resistances, across theterminals of the dynamo. so that the relay opens the short-circuit upon the attainment in t-he generator, thus throwing the resistance 5 into operation and regulating the voltage of the generator output in a wellnown manner.

Three resistance-devices are employed in connection with the winding .of the rela-y, for the purpose of compensating for variations in temperature, whether of the atmosphere or due to the direct heating effect of the electric current upon the relay-winding. One of these resistance-devices 8 is immediately in series with the winding 2. This device is made 0f some material having a substantially lower temperature coefcient of resistance than the copper winding of therelay. Preferably its coefficient should be apof a predetermined voltage proximately zero, and for this purpose the material known as thurld has been found suitable. The second resistance-device 9 has a comparatively high 'temperature coefficient, and this device may conveniently be made of coplper .wire the same as the winding of 2 the re ay. This reslstance-device 9 1s connected in circuit parallel with both the wind# he third resistance-device 10, which consists of thurlo or other materiall of low temperature coefficient, vis arranged in series ing?, and the resistance-device 8.

with the two arallel portions of the circuit.

already descrl ed. This resistance-device is shown as connected, by a wire 11, with one of the main conductors 12 from the dynamo, the other main conductor 13 being connected, by a wire 14, with the common terminal of the resistance-devices 8 and 9.

The rela -winding and the resistance-device 9 shou d be so associated as to be always at substantially the same temperature, and a means for this purpose is indicated in the diagram as having the form of la casing 15 constituting a common inclosure for these parts. The resistance-devices 8 and 10 are shown as inclosed in the same casing, but

this is not essential where thedevices are ofmaterial having an approximately zero temperature coefficlent.

The operation of the compensating-devices may be described as follows: The total resistance of the resistance-devices and the relay-winding increases, with an increase of temperature, ata much lower ratio than in thecase of a winding of copper wire alone,

owing to the presence of the resistance-device 10, and accordingly the fiow of current at a given voltage is not greatly diminished by such rise in temperature. The current, which divides between the resistance-device 9 and the resistance-device 8 and the winding 2, is distributed between these two branches of the circuit inl accordance with their relative resistances. v*With any rise in temperature the resistance ofthe device 9 increases more rapidly than that of the par-l allel portion of the circuit, owing to the fact that the latter consistsonly partly of material of a high temperature coefficient.

Accordingly, a rise in temperature results 1n an increasedproportion of the current passing through the relay-winding 2, thus compensating for the diminution in the total amount of thecurrent.

By a suitable proportioning and selection of materials it has been found that a practically perfect compensation maybe secured for any ordinary lrange of temperatures. By varying the proportions and materials an arrangement'may be producedwhich will either over or under compensate, as circumstances render desirable. Where exact compensation is required it'has been found that this result may be secured by -of the parts ance 9 of ordinary copper wlre and the resistance-devices 8 and 10 of thurlo, the resistances of the parts 2, 8, and 10 being approximately equal, while the resistance of the part 9 is 25%-less.

The present invention has the advantage, among others, that it disposes with the use of thermostatic devices and mechanisms of all kinds, and also that it does not call for the use of material having a negative tem perature coefficient of resistance.

It will be apparent that the mvention is A suitable for use with electric instruments and devices of Various kinds, and that lt is not limited to the use of the particular resistance-materials specified in the preceding description.

The invention claimed is: 1. The combination, with an electric instrument having a conductor with a comparatively high temperature coefficient of re-' sistance, of compensating devices comprising: a resistance-device, of low coefficient, in series with said conductor; a resistancedevice, of high coefficient, in parallel with said conductor and the first-mentioned resistance-device; and a third resistance-de vice, of low coefficient, in series with the parallel-connected parts beforementioned.

2. A combination, as in claim 1, in which the respective resistances, at normal temperatures, of said conductor and the two resistance-devices of low coefficient are approximately equal, while the resistance of the device of high coefficientl is approximately three fourths as greatf- 3. The combination, with an electric instrument'having a winding, of compensating devices comprising: a resistance-device,

havin a substantially lower temperature coefliclent than said winding, arranged in series therewith; a second reslstance-device, having a coefficient not substantially lower than that of said winding, in parallel with -the winding and the first-mentioned resistance-device; and a third resistance-device,l of substantially lowercoefficient than that of said winding, in series with thel parallelconnected parts beforementioned.

4f. The combination, with an electric instrument havinga winding of copper wire,

coefficient substantially lower than that of copper, in series-with said winding; a resistance device, connected in parallel with the -of a resistance-device, having a temperature winding and the first mentioned resistancev device, having a coefficient higher than the joint coefficient of the winding and the firstmentioned resistance; and av resistance deff -vice in series with the before mentioned parallel branchesof the circuit, the last-mentioned resistance-device having a coefficient lpwer than that of cop er.

RAYMON H. SULLIVAN. 

